Breather plug for electric motors



June 17, 1947. n. H. MANNEY 22,890

BREATHER PLUG FOR ELECTRIC MOTORS Original Filed Nov. 24, 1941 2 Sheets-Sheet 1 IHVENTOR Dav/0 MHNNEY ms ATTORNEYS- D H. MANNEY BREATHER PLUG FOR ELECTRIC MOTORS June 17, 1947.

Original Filed Nov. 24, 1941 2 Shan -Shut 2 mvzmon 067 WB H. MHNHEY v TQLAW QAU H I! ATTORNEYS Reissued June 17, 1947 BREATHER PLUG FOR ELECTRIC MOTCRS David H; Manney, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Original No. 2,323,146,

This invention relates to an improved protectlve device for electric machines and especially electric machines or electric motors used in a. substantially inflammable atmosphere in which fire or explosion might take place as a result of sparking in the machine or motor.

Electric machines and Particularly electric motors are commonly used as driving means for gas or gasoline pumps, apparatus in coal mines, chemical works or other plants where dust-laden air or atmosphere charged with inflammable or explosive gases or vapors are invariably present. If an ordinary open type motor is used under such circumstances, the charged atmosphere in and surrounding the motor may readily be ignited by sparking at the brushes, collector rings or any other part of the motor capable of an electric discharge tending to produce a spark, thus resulting in much damage and perhaps disastrous fire or explosion. To avoid this, special motors are available, these motors having casings or housings with predetermined clearances between parts comprising the housing, said clearances prodated June 29, 1943, Serial No. 420,215, November for reissue May 1, 1945, Serial No. 591,241

Application 6 Claims. (Cl. 17236) establish communication between the interior and exterior of the housing. The provision of such plugs thus eliminates the necessity of maintaining machine operations upon interfltting parts of the motor casing within suchrexceedingly close limits, for the plugs in the present instance provide the breather elements instead of the carefully designed ducts or spaces formed between inter-fltting parts or the motor housing.

The breather plugs of the present invention are made from a sintered, non-compacted metal powder. presenting an indefinitely large number of small and tortuous paths or ducts through which atmosphere may be drawn into or ejected from the interior of the motor housing. These plugs with their small and tortuous paths or ducts prevent the propagation of flame from the motor housing in case an inflammable or explosive atmosphere or gas, drawn into and filling the motor, has been ignited by sparking within the motor housing.

The character of the plugs and especially the tensile strength of the metal particles comprisviding communicating ducts between the interior and exterior of the housing which act as breather openings of such dimensions as to prevent flame propagation from the interior to the exterior of the motor housing in case the charged air orgas within the motor is ignited by sparking therein.

To produce motors provided with such breather spaces or ducts between interfltting parts forming the motor housing requires careful and tedious machining and working at close tolerances, for-i! such spaces or ducts are too small, explosions within the motor cannot properly be relieved.

The restriction offered by too small ducts or spaces-would unduly subject the motor to the forces of the explosion therein, which would result in damage thereto and in some instances might even cause bursting of the motor casing thereby resulting in igniting of the surrounding'charged atmosphere. i 1

In case the spaces or ducts lust referred to are too large, proper impedance to flame propagation would not be offered, in which instance the motor would of itself not be damaged, but again the exterior, charged atmosphere would be ignited.

-Tnus' it may be seenthat such breather spaces or clearances must necessarily be maintained within exceedingly close limits, requiring thereforetedious and careful machining of inter-fitting parts of the motor casing. v a

It is among the objects of thepresentinvention to provide an electric motor having a sealed casing'or housing with a breather plug or plugs which 1' tion.

ing the plugs are suchthat high resistance to fracture, caused by pressure resultingeither from explosion or freezing of condensed moisture,

within the'piug, is provided; Thus the possibility of reducing or even entirely destroying the protective function of a breather element for the casing of an electric motor such as commonly used fibrous packing, porous plastics, ceramics or porcelain and'the like, which are destructible and fragile underconditions mentioned, is substantially eliminated by the present type 0f plug which is adapted to withstand high pressure and continue its protective function under the most adverse circumstances. I o

The plugs of the present invention are adapted to be used not only for the prevention of flame propagation, but function also as drain plugs, permittin condensed moisture to be elected from within the casing and also as filters for thelubricating system of the device.

Further objects and advantages of the present invention will be apparent from the follow ing descriptiomreference being had to the acv companying drawings wherein a preferred em-, bodiment of the present invention is clearly shown. I 1 l In the drawings;

Fig. 1 is a fragmentary electric or motor equipped with the present inven- Fig. 2 is a longitudinal view, partly section,

sectional view of ,an

. II, which may be showing the invention Fig. 3 is a fragmentary view or still another I type of motor equippedwith the present invention.

Figs. 4 and 5 are enlarged sectional views showing the detailed construction of plugs comprising a body of sintered, non-compacted metal powder Referring to the drawings and particularly to Fig. 1, the numeral 20 designates the housing or casing of the electric motor. Pole shoes 2| are supported within the housing carrying the field windings 22. A rotor or armature 23 is rotatably supported by the motor shaft 24 journalled in sleeve bearings II and Il, said'bearings being held in coaxial alignment within the housing 20 in any suitable manner.

The housing 2| has an inwardly extending cone-shaped shell portion 21 forming an interior chamber which is in communication with the outside of the motor housing through a neck or pas- .sage II. This chamber comprises two compartments, the on designated by the numeral termed the lubricating oil reservoir, the compartment 30 which may be {termed the sump" reservoir 29. Both these compartments, the reservoir I! and the sump 30, are in communication with each other. Fibrous material of any suitable type designated by the numeral 30a is placed within these compartments, this fibrous material being soaked with the lubricant, the fibrous materlal in the sump acting as a wick to lift the lubricant from th sump up to the reservoir. Openings in the bearings 25 and 16 permit this fibrous material to contact with the exposed portion of the rotating armature shaft 24 and th'ereby direct the lubricant upon the shaft. A duct ll provides communication between the reservoir compartment 29 and the sump compartment lll so that lubricant flowing along the shaft through the bearing therethrough and enter the sump 30 from where said lubricant will again be lifted by the fibrous material into the reservoir 29, thus creating a lubricant circulating systems With the bearing 2' in the opening of the cone-shaped shell 21 and the shaft 24 in the bearing it that the interior of the motor casing 20 containing the field and armature and containin also the usual brushes or collector ring mechanism, not shown in the present drawings, is completely shut off or isolated from the chamber containing the lubricant charged fibrous material 3|. In the duct II there i provided a plug or the present invention, this plug assembly being designated by the numeral 4|). In the drawing it may be seen that the plug is located in the duct between the sump 30 and the other end of the duct whichcommunicates with the reservoir portion I! through the clearance spaces provided between the bearing 25 and the shaft 24. This plug 44 is of the type as designated in the Fig. 4 and comprises a sleeve 4| exteriorly threaded so as to be threa'dedly received by the portion 42 of duct ll. The sleeve 4| is counterbored as at 48 to receive the body of sintered noncompacted metal powder 44. This plug portion 44 may be formedfrom any number of metal powders such 'as copper and tin powders, copper and nickel powder, iron powder and copper or other suitable powdered metals and may include small quantities of non-metallic materials such as graphite and the like. The method of ma n 25 may enter duct 3|, flow may readily be seen be ignited by sparking or for the lubricant containing Koehring, April the sintered, such a character that it provides indefinitely large number of small and tortuous paths or ducts through which fluids may pass. Thus the presence of this porous metal plug 4| in the oil. conducting duct ll of the motor acts as a filter for the oil passing through duct Ii to" the oil sump 30.

This porous. non-compacted metal plug also acts as an arrester for preventing the propagation of flame passing through the duct 3| toward the oil containing sump 30 and reservoir II and in communication through the neck or opening by a Welsh plug 28a. If a motor is used in an installation surrounded by a charged atmosphere. that is, an atmosphere laden with an explosive or combustible dust or gas, any ventilatingair so charged and drawn into the motor may readily the brushes, collector rings or any part of the electric motor capable of giving off a spark. Such explosion will, due to its pressure, tend to thrust the flame through any opening it may flnd, as for instance through the clearance space between the shaft 24 and the inner end of the bearing-25 so that this flame could be directed into duct II and therethrough into the lubricant containing chambers 29 and 30 if no impedance were provided in the duct. However, with the provision of the porous metal plug 40 in duct 31, which provides innumerable small and tortuous paths, the propagation of the flame from duct 3| and its portion 42 through the plug 40 is entirely eliminated, for the small tortuous paths, will not permit the flame to pass therethrough and into the lubricant containing chambers 30 and 29. .Thus the possibility of flame within the motor escaping to the exterior of the motor to ignite surrounding charged atmosphere is substantially eliminated.

Another porous plug "is screw threadedly received in an opening 5| in the casing 20 of the motor providing direct communication between the exterior of the motor and the interior portion thereof containing the fields, armature and brushes or collector ring mechanism thereof. This-plug ill is of the type shown in the Fig. 5 where a flanged collar 52, exteriorly threaded, has an elongated plug 53 made from sintered, non-compacted metal power of the same character as plug 40. This plug it permits the motor to breathe ventilating air into its interior, and like plug 40, prevents flame propagation from the interior of the motor to the exterior thereof in case an explosion occurs within the motor. Another plug 60 of the same type as plug 60, is provided in an opening 62 at the bottom of the motor casing 20, this plug 60 providing an exit for any condensed moisture that may gather at the bottom of the motor, this plug also preventing any flame propagation in case of an explosion within the motor. as

From the aforegoing it may be seen that the motor as illustrated in Fig. 1 has three porous metal plugs 40, 50 and 60. all having a-eommon function, that is the function of preventing flame propagation from the interior of the motor to the exterior thereof in case an explosio occurs within the motor. The plug 4! acts also as an oil filter and the plug 50 has an additional function of providing a breather permitting ventilat- 28 normally closed with the outside of the metal V pump or some driving element for gas or gasoline pumps, superchargers or the like. In driving gasoline pumps or superchargers a motor of this type forms a .part of the equipment used on an airplane and in certain instances, especially when reaching high altitudes, is subjected to extremely low freeling temperatures. This motor comprises ahousing ll, an armature II, a commutator 12 thereof being provided with the usual brush mechanism, not illustrated in the present instance. This armature has a shaft 15 supported by two rolier'bearings l3 and I4 carried in the housing. The end of the armature shaft is is connected to the driven element which may be a gas pump, a supercharger or the like, said gas supercharger flammable and explosive gases which ofltimes flnd their way along the shaft and into the interior of the motor. Buch gases within the motor are readily ignited by any sparking that might 4 occur at the brush mechanism and in some instances an explosion within the motor takes place which, if the flame thereof is permitted to be propagated and find its way outside of the motor would cause explosions. In order to eliminate sometimes giving 'ofl in- 16 in case exploding. gases'flnd their way from th mechanism driven by shaft II through the housing portion II into chamber ll thereof and from there are introduced into the interior of the motor by the forced ventilating air, these two plugs I! and Ill will prevent flame propagation should such inflammable atmosphere within the moto'rbe ignited by sparking at the the commutator or any other place motor.

brushes on within the In Fig. 3 is illustrated a fragmentary portion of a motor in which the air circulating mechanism in the form of a fan 90 is within the motor and driven by its rotating part directly. In

this instance fan it causes air to be drawn into the motor through a plug 8| like that shown in Fig. 5 this air passes around the fleld' windings 92 of the. motor and other parts to cool them and finally exiting from the interior of the electric motor through plug 93 identical with the plug shown in Fig. 4. Plugs SI and ll thus act as breather-s capable of preventing any flame propagatiori resulting from an explosion within the such flame propagation, motors of this type are usually ventilated by a forced air circulation being .directed into the motor in any suitable manner. In the construction shown in Fig. 2, a duct OI leads to the exterior of the motor and has a pipe 18 connected thereto which is connected to either a suction or a pressure pump adapted to draw air from the motor through duct or on the other hand force air through duct 85 into the motor. This duct 65 leads into a chamber 11 formed in the end housing 18 of the motor. In .one end of said chamber the roller bearing ll is provided. In this chamber there is provided also a porous metal plug between duct 65 and bearing II, this plug comprising an outer sleeve Ii which contains the porous metal plug body I2 made from a sintered, non-compacted metal :2, the shaft 15 of the armature extending through this elongated tube 83 which has a rotating flt about said shaft. A duct or passage II is provided on the outside of ball bearing 14, I this duct connecting the space outwardly of the bearing with the interior of the motor casing so that ventilating air passing from duct 65 through the porous plug 82 may enter the interior of the motor through duct it instead of passing through the ball bearing II.

In any suitable location in the housing of the motor, preferably adjacent the bottom thereof, a plug I60 is provided in an opening in said inotor housing, this plug I50 being of the type illustrated in the Fig. 5 and therefore having an elongated body made from a sintered non-compacted metal powder. The plug I50 acts as an egress for the ventilating air of the motorcasing when the pressure pump connected with pipe it forces the air down into the duct 65. Where a suction pump is connected with pipe 18 plug ilii acts as an entrance for air into the interior of the motor casing 10. In case such ventilating airisofan might be adopted, all coming within the scope of motor housing.

The device shown in Fig. 2 is, as has been said, at times subjected to very low freezing temperatures especially when the plane upon which it is used is traveling at high altitude. Any condensation which might take place within the motor and which might accumulate in plugs 82 and v I" wound be formed into ice in said plugs, the

freezing of said moisture resulting in a terriflc pressure being exerted upon the particles making up the porous plugs. Innumerable experiments have been made in connection with these plugs, and during these experiments said plugs were laden with water and subjected to as low as 40 below zero Fahrenheit andin each instance no damage resulted. These tests also showed this type of plug as being capable of withstanding extremely high pressure caused by the forcing of air or atmosphere therethrough due to an explosion. In none of these experiments to which these plugs were subjected was the plug injured in any manner such as to prevent complete functionlng thereof. Thus it may be seen that these porous plugs made from a sintered, non-compacted metal powder, are comparatively strong, bein capable of withstanding extreme pressures such as are exerted in case of moisture within the plugs being frozen or the forcing of atmosphere under pressure as the result of an explosion.

'Fibrous materials, porous plastics, ceramics or porcelain and the like when used under such circumstances do not provide sufllcient strength to withstand the extreme pressure and tend to fracture or crack when subjected thereto, thereby entirely destroying the function for 'which they are intended in any instance of this kind. Fracture of a plastic in any installationas disclosed in the drawing would necessarily permit flame propagation from the interior to the exterior of the motor thereby permitting flames resuiting from an explosion within the motor to be directedexteriorly of the motor and ignite the surrounding inflammable or explosive atmosphere, thusresulting in a damaging and dangerous fire or explosion outside the motor.

' While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms v the claims which follow.

What is claimed is as follows:

1. In combination with an electric machine having a sealed casing. 01 a breather plug insaid casing adapted to prevent the propagation 01' name caused by the explosion 01 gas vapors ignited by sparking in the interior oi the casing, said breather plug comprising a body consisting oi' sintered, non-compacted metal powder.

2. In combination with an electric machine having a sealed casing, 01 a porous metal plug in said casing providing for the transi'er or air into and out of said casing, the draining or any moisture within the casing due to condensation and for the prevention of name propagation caused by the explosion of gas vapors ignited by sparking within the casing of the electric ma chine, said' plug comprising an elongated body consisting oi sintered, non-compacted metal powder.

3. An electric machine having a casing providing bearings; an operating shai't supported in said bearings; an oil reservoir in the casing; an oil sump in the casing; an oil conducting duct leading from one bearing in communication with the reservoir to the sump; a porous metal plug in said duct between the bearing and the sump for preventing the propagation of flame to the 011 containing sump and for filtering the oil; and a second porous metal plug in the casing of the electric machine, providing both a breather for said casing and a means for preventing flame propagation caused by the explosions of gas vapors ignited by sparking in the interior of the electric machine, both of said porous plugs being made from a sintered, non compacted metal powder. I

4. In combination with an electric motor provided with a sealed casing, a 'duct leading into new said casing for the introduction 01' a forced current 01' air into the casing; second a duct in the casing providing for the egress oi said air: a plug in each duct, each plug comprising a body consisting or sintered, non-compacted metal powder providing an indefinitely large number 01' small and tortuous paths or ducts through which the air passes and which prevent the propagation of flame resulting from the igniting of an inflammable or explosive atmosphere drawn into and flllingthe motor casing.

5. A rotary electric motor having a casing at least a portion or which comprises a body co sisting oi sintered, non-compacted metal powder said portion of the casing providing a ventilator for the motor which prevents flame propagation. 8. An electric machine which inherently sparks during operation thereof including a sealed casing therearound, at least a portion 01' said casing comprising a ventilator consisting of sintered non-compacted metal powder, said ventilator permitting inhalation and exhalation of gases into and out of the casing and simultaneousiy preventing flame propagation therethrough.

DAVID H. MANNEY.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 522,972 Cuttriss July 17, 1894 2,017,491 Gloveacki Oct. 15, 1935 

